It has a short, rounded head, obtuse muzzle, small bead-like eyes, and short rounded ears, nearly concealed by the fur.
The last premolar and the molars have quadrate crowns, provided with two strong transverse ridges, or with four obtuse cusps.
Following Euclid, a right angle is formed by a straight line standing upon another straight line so as to make the adjacent angles equal; any angle less than a right angle is termed an acute angle, and any angle greater than a right angle an obtuse angle.
The triangle is here an irregular one, consisting of a narrow base to which one end of the string was fixed, while the second side, forming a slightly obtuse angle with the base, consisted of a wide and slightly curved sound-board pierced with holes through which the other end of the strings passed, being either knotted or wound round pegs.
Roughly calculated, two-fifths of the total area of Bolivia is comprised within the Andean cordilleras which cross its south-west corner and project east toward the Brazilian highlands in the form of a great obtuse angle.